Glossary - Infectious Diseases

Acquired immune deficiency syndrome (AIDS) - a disease caused by the human immunodeficiency virus (HIV), which kills or impairs cells of the immune system and progressively destroys the body's ability to fight infections and certain cancers. HIV is most commonly spread by sexual contact with an infected partner. The term AIDS applies to the most advanced stages of an HIV infection.

Alcohol-induced chronic hepatitis - one type of hepatitis; continued liver damage throughout the liver from heavy alcohol consumption.

Antibody - a special protein produced by the body's immune system that recognizes and helps fight infectious agents and other foreign substances that invade the body.

Chickenpox - a highly viral infectious disease, usually associated with childhood. By adulthood, more than 95 percent of Americans have had chickenpox. The disease is caused by the varicella-zoster virus (VZV). Transmission occurs from person-to-person by direct contact or through the air.

Chlamydial infection - very common sexually transmitted disease or urinary tract infection caused by a bacteria-like organism in the urethra and reproductive system.

E. coli O157:H7 (also called E. coli. or Escherichia coli) - Species of bacteria found in the intestines of man and healthy cattle; often the cause of urinary tract infections, diarrhea in infants, and wound infections.

Genital warts (also called venereal warts or condylomata acuminata) - caused by a virus related to the virus that causes common skin warts. Usually, genital warts first appear as small, hard, painless bumps in the vaginal area, on the penis, or around the anus.

Gonorrhea - a common sexually transmitted disease caused by a bacterium, which can lead to infertility in women.

Hepatitis - inflammation of the liver that sometimes causes permanent damage; caused by viruses, drugs, alcohol, or parasites. Hepatitis has the following forms:

Hepatitis A - a form of infectious hepatitis caused by the hepatitis A virus. The virus may be spread by fecal-oral contact, fecal-infected food or water, and may also be spread by a blood-borne infection (which is rare).

Hepatitis B - a form of infectious hepatitis caused by the hepatitis B virus. Transmission of the hepatitis B virus occurs through blood and body fluid exposure such as blood, semen, vaginal secretions, or saliva.

Hepatitis C - a form of infectious hepatitis caused by the hepatitis C virus. Transmission of the hepatitis C virus occurs primarily from contact with infected blood, but can also occur from sexual contact or from an infected mother to her baby.

Hepatitis D - a form of infectious hepatitis caused by the hepatitis (Delta) virus. This form of hepatitis can only occur in the presence of hepatitis B. Transmission of hepatitis D occurs the same way as hepatitis B.

Hepatitis E - a form of infectious hepatitis caused by the hepatitis E virus. This form of hepatitis is similar to hepatitis A. Transmission occurs through fecal-oral contamination. Hepatitis E is most common in poorly developed countries and is rarely seen in the US.

Hepatitis G - the newest form of infectious hepatitis. Transmission is believed to occur through blood and is seen in IV drug users, individuals with clotting disorders, such as hemophilia, and individuals who require hemodialysis for renal failure.

Herpes genitalis - an infection caused by the herpes simplex virus (HSV) and usually spread by sexual contact. Symptoms may include painful blisters or open sores in the genital area, which may be preceded by a tingling or burning sensation in the legs, buttocks, or genital region. The herpes sores usually disappear within a few weeks, but the virus remains in the body and the lesions may recur from time to time.

Herpes zoster (shingles) - a viral infection of the nerves, which results in a painful rash of small blisters on a strip of skin anywhere on the body.

Human papillomaviruses (HPVs) - viruses that can cause warts; some HPVs are sexually transmitted and cause wart-like growths on the genitals. HPV is a major risk factor for cervical cancer.

Malaria - a disease caused by a parasite that is transmitted person-to-person by the bite of an infected Anopheles mosquito. These mosquitoes are present in the tropics and subtropics in almost all countries. Malaria is the most deadly of all tropical parasitic diseases.

Mastitis - inflammation of breast tissue.

Measles - a very contagious viral illness characterized by a distinct rash and a fever; spread through airborne droplets of nasal secretions.

Meningitis - an inflammation of the membrane that covers the brain and spinal cord.

Mumps - an acute and highly contagious viral illness that usually occurs in childhood. Spread by airborne droplets from the upper respiratory tract, the disease usually takes two to three weeks to appear.

Pertussis (also called whooping cough) - mainly affects infants and young children; caused by a bacterium, it is characterized by paroxysms of coughing that end with the characteristic whoop as air is inhaled. Pertussis caused thousands of deaths in the 1930s and 1940s, but with the advent of a vaccine, the rate of death has declined dramatically.

Pleural effusion - a collection of fluid between the lung and chest wall.

Pneumothorax - air becomes trapped in the pleural space (the area between the lung and the chest wall); causes the lung to collapse.

Poliomyelitis - a highly contagious infectious disease caused by various types of poliovirus. Spread though feces and airborne particles, the poliovirus usually causes no more than a mild illness. However, some of the more serious manifestations of the disease include meningitis, which can lead to extensive paralysis.

Respiratory diphtheria - when a person is infected with diphtheria, the bacterium usually multiplies in the throat, leading to the respiratory version of diphtheria. A membrane may form over the throat and tonsils, causing a sore throat. Other common symptoms of respiratory diphtheria may include: breathing difficulty, a husky voice, enlarged lymph glands, and an increased heart rate.

Rubella (also called German measles) - an acute viral infection that causes a mild illness in children and slightly more severe illness in adults. The disease is spread person-to-person through airborne particles and takes two to three weeks to incubate.

Skin (cutaneous) diphtheria - one type of diphtheria; the symptoms are usually milder and may include yellow spots or sores (similar to impetigo) on the skin.

Syphilis - the initial symptom of syphilis is a painless open sore that usually appears on the penis or around or in the vagina. If untreated, syphilis may go on to more advanced stages, including a transient rash and, eventually, serious involvement of the heart and central nervous system.

Tetanus - an acute, sometimes fatal, disease of the central nervous system; caused by the toxin of the tetanus bacterium, which usually enters the body through an open wound. The tetanus bacterium live in soil and manure, but also can be found in the human intestine and other places.

Transverse myelitis - inflammation and swelling along the spinal cord with motor or sensory nerve dysfunction.

Tuberculosis (TB) - an infectious disease that was once a major killer worldwide. The predominant TB organism is Mycobacterium tuberculosis (M. tuberculosis). Spread person-to-person in airborne droplets caused by sneezing or coughing, the bacteria usually infects the lungs. However, due to improved nutrition, housing, sanitation, medical care, and the introduction of antibiotics, reported TB cases in the US have declined dramatically.